1. Field of Invention
This invention relates to nanofibrous membranes and, more specifically, to nanofibrous membranes for a disposable biosensor.
2. Description of the Related Art
Diabetes is an increasingly important worldwide public health problem. The metabolic disorder results from either insulin deficiency, in type 1 diabetic patients, or from insulin resistance and its complications in type 2 patients. Both conditions can result in hyperglycemia leading to blood glucose concentrations higher than the normal range 80-120 mg/dL (4.4-6.6 mM). The diagnosis and management of diabetes require the careful monitoring of blood glucose levels. The glucose bio-sensor has thus become one of the most important physiological monitoring devices, accounting for about 85% of the entire biosensor market.
A biosensor is a device which combines an immobilized bio-recognition element with a transducer. It can monitor chemical substances on the inside or outside of an organism by generating a signal representative of the analyte's concentration after coupling the biochemical and transducer reactions. Glucose biosensors are based on electrochemical principles and frequently employ enzymes as the biological recognition element. The biosensor's performance and sensitivity often strongly depend on the influence imposed on the enzyme's structure by immobilization. Such influences result from the choice of the host molecule and the immobilization method used.
In attempts to retain enzymatic activity and stability various molecules have been used to immobilize enzymes on different substrates, e.g. poly(vinyl alcohol) (PVA), poly(ethylene oxide) (PEO), chitosan, polymethylmethacrylate (PMMA), poly(vinyl pyrrolidone) (PVP) and polyurethane (PU). PVA is often used as an immobilization matrix because of its inherent nontoxicity, high thermal stability, good biocompatibility and its desirable physical properties such as its elastic nature, good film forming properties, and its high degree of swelling in aqueous solutions—all of which contribute to making it a good matrix for enzyme immobilization. Different methods, such as the cross-linking of PVA, freeze-thawed PVA, and enzyme encapsulation in PVA/silicate hybrid materials, have been successfully employed to immobilize the enzyme molecules in various membranes. However, due to the compaction and low-conductivity of the PVA membrane, substrate infiltration and electron transfer between the enzyme membrane and the electrode remain problematic.